Abstract:

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The purpose of this study was to determine the effect of sintering conditions on
microporosity of and cell proliferation and bone ingrowth on biphasic calcium phosphate (BCP)
bioceramics. Discs were prepared from a calcium-deficient apatite preparation that upon sintering at
1050oC and above, results in a BCP with 60% hydroxyapatite (HA)/ 40% beta-tricalcium
phosphate (β-TCP) ratio. The discs were divided into groups which were sintered under different
conditions of heating rate (programmed vs. non-programmed) and temperature (1050°C vs.
1200°C). The discs were characterized in terms of composition (HA/β-TCP ratio), surface
morphology, surface area, surface microporosity, per cent microporosity, and dissolution properties.
The in vitro effect of sintering conditions on cell proliferation was determined using an established
mouse fibroblast cell line (L929). Results demonstrated the following: (a) the HA/β-TCP ratio
remained 60/40 regardless of sintering conditions; (b) the % microporosity, surface microporosity,
surface area of the BCP and cell proliferation on the BCP significantly decreased with increasing
sintering temperature, and (c) the extent of dissolution decreased with decreasing per cent
microporosity. The in vivo study indicated no tissue adverse reaction and direct bone contact with
the implant surface, confirming the biocompatibility of the BCP bioceramics. Resorption of the
BCP and bone ingrowth was directly related to the sintering temperature: the higher the
temperature, the lower the resorption and the bone ingrowth. Results of this study indicate that per
cent microporosity of the BCP bioceramics affects its dissolution properties and cell response. The
study demonstrates that optimum per cent microporosity elicits optimum cell response and should
be considered to provide osteogenic/osteoinductive property to bioceramics.

Abstract: The development of calcium phosphate ceramics and other related biomaterials for bone graft
involved a better control of the process of biomaterials resorption and bone substitution. The
biphasic calcium phosphate ceramics (BCP) concept is determined by an optimum balance of
the more stable phase of HA and more soluble TCP. The material is soluble and gradually
dissolves in the body, seeding new bone formation as it releases calcium and phosphate ions
into the biological medium
The main attractive feature of BCP ceramic is their ability to form a direct bond with the host
bone resulting in a strong interface. The formation of this dynamic interface is the result of a
sequence of events involving interaction with cells; formation of carbonate hydroxyapatite
CHA (similar to bone mineral) by dissolution/precipitation processes. At the present time,
BCP is commercially available in blocks, particulates, customized design. The need of
material for Minimal Invasive Surgery (MIS) induced the development of a concept of
granules combination with polymer or calcium phosphate cement for injectable/mouldable
bone substitutes. Four types of injectable/mouldable bone substitutes have been developed by
INSERM Nantes University.

Abstract: Microporosity and granules size are important parameters for the development of
suspension, composites and injectable bone substitutes. In this experimental study performed in a
rat bone model of critical size defects, were have determined the kinetics of bioceramic resorption
and bone ingrowth. Two kinds of granules (1mm in diameter) of Biphasic Calcium Phosphate BCP
(60/40 HA/TCP ratio) with 20% and 40% microporosity of less of 5 microns in size, were used.
Higher bone ingrowth was observed for low porosity (LP) at 3 weeks versus high porosity (HP); the
contrary was measured after 6 weeks. About the kinetics of BCP resorption, significant difference
between the 2 porosities was noticed, the higher for high microporosity. High porosity on time,
promotes more bone ingrowth at the expense of the bioceramic than lower microporosity.

Abstract: The research on ceramic scaffolds for bone tissue engineering is, nowadays, one of the
newest and most attractive topics in the field of materials for biomedical applications.
These scaffolds are aimed to provide supporting or even enhance the reparative capacity of
body. Biphasic calcium phosphates (BCPs) and silicon doped BCP are very interesting
candidates to be used as materials for scaffolds fabrication in bone tissue engineering.
BCPs and silicon doped BCP consist of a mixture of hydroxyapatite (HA) and β-tricalcium
phosphate (β-TCP) or HA and α-tricalcium phosphate (α-TCP), respectively. For the
regenerative purposes BCPs show better performance than HA because of the higher
solubility of β-TCP compound, which facilitate the subsequent bone ingrowth in the
implant. On the other, silicon doped BCP involve silicon that substituted into the apaptite
crystal lattice for phosphorous with the subsequent charge imbalance. HA/α-TCP based
bioceramics exhibits an important improvement of the bioactive behaviour with respect to
non-substituted apatites. This work reviews the procedures to synthesise and fabricate
scaffolds based on HA/β-TCP and silicon stabilised HA/α-TCP. Special attraction has
been paid in the different synthesis methods and to the shaping of final scaffolds. By
knowing the scaffold features at the crystallinity and macrostuctural level, the
biocompatibility and clinical performance can be better understood, which will be also
considered in this review.